Vacuum-tube apparatus and method of controlling- same



Jan. 17, 1928. 1,656,187-

' C. L. FARRAND VACUUM TUBE APPARATUS AND METHOD OF CONTROLLING SAME Filed June 1913, 2 Sheets-Sheet 1 ENTOR 57m x O Z EYMM A v Q Jan. 17,1928. 1 1,656,187

, C.'L.FARRAND VACUUM TUBEAPPARATUS AND METHOD OF CONTROLLING SAME Filed June 14, 1e19 2 Sheets-Sheet 2 INVENTOR ATTORNEY Patented Jan. 17, 1928.

UNITED STAIES PATENT OFFICE.

CLAIR L. FARRAND, 0F ELIZABETH, NEW JERSEY, ASSIGNUR, BY MESNE ASSIGN- MEN'IS, '10 RADIO CORPORATION 013 AMERICA, A CORPORATIUN OF DELAWARIG.

VACTLTUM-TU13E AYIARATUS AND MEtllI-IOTD SAME.

Application filed June 14, 1919. Serial No. 3%,.289.

This invention relates to radio signaling apparatus and devices, but more particular ly to improvements of apparatus utilizing vacuum tubes both for transmission and reception in radio telegraphy and telephony.

The invention is applicable to vacuum tubes whether used as regenerative devices or amplifiers, and the prii'nary objects of the invention are to increase the eiliciency of such devices, render them more sensitive, and enable the electron discharge to be con trolled in a more regular manner and consequently the amplifying action of low frequency currents, thus rendering the devices con'iparatively free from distortion.

l have chosen to illustrate one form of my invention in connection with the Weagant shield valve or outside element valve, as disclosed in his U. S. Patent No. 1,289,981, granted December 31, 1918, in which the shield or influencing member is located out side of the evacuated container, but I am not to be understood as limiting the invention to this type of valve, because the invention is applicable to vacuum tubes in which all three elements are contained within the vessel.

in operating the Weagant type of valve as a low frequency amplifier for instance, for transmitting and receiving, I have found that the improved results herein specified are obtained by impressing a high frequency voltage upon the outside shield or influencing member. My present view is that the results obtained can be explained on the as sumption that the application of a proper value of oscillatory potential to the shield results in a control and regulation of a definite negative charge imparted to the inner surface of the glass by the electron discharge within the tube. This negative charge will be controlled by the positive charge on the external controlling member produced by the high frequency voltage. Any positive charge from the high frequency source will discharge through the valve to the filament but the discharge of the negative charge can only occur through the glass so that a negative potential is easily accumulated. In a radiophone transmitter for instance, using the valve as an amplifying modulator, I have found that the addition of the high frequency voltage produces greatly l111- proved modulation.

In an amplifier, the additional source of potential supplying the influencing member should preferably be above audio frequency. and in a detector although the applied n2; quency should preferably be higher than the working frequency, it may be equal to or less than the working frequency, but should always be above audio frequency.

in practicing my invention, the additional source of potential applied to the influencing member may be a suitable generator of alternating current, or in the of a transnntter, may be the generator supplying the power for t 'ansmission.

My invention is illustrated in the accompanying drawings in which,

Fig. l a diagrammatic representation of a radiophone transmitter embodying the invention 2 is a similar view of a vacuum valve used as a detector;

Fig. 3 is a similar view of an amplifier; and

Fig. at is a view of a modification.

Referring to the drawings, and at first more particularly to the radiophone transmitter shown in Fig. l, A represents an antenna connected to ground at B through the usual inductance or coupling coil C. The oscillating valve 1) and theamplifying valve 1) in this instance are each shown of the same type, with the usual heated element or filament E and the cold element or plate F within the evacuated glass container G, and the ini'luei'icing member in the form of a metallic shield H around the outside of the container. The electrostatic field due to the influencing member H is at an angle to the electron stream within the container, as described in U. S. Patent No. 1,289,981. The filaments E are energized by the usual batteries J. The oscillating valve D need not be of the shield type, but is conveniently so shown for purposes of illustration, it being understood that in a radiophone such as represented in Fig. 1 the valves may be all of the same type or of different types.

The source of energy K is shown in this instance as a generator, instead of the usual plate battery, and this generator K is preferably shunted bya condenser L for its protection. The transformer O is for the usual purpose of applying the low frequency energy from the amplifier valve I) to the oscillator l). The choke coil 1? is preferably placed between the oscillator and modulator in order to reduce the tendency of oscillating currents to fioW through the modulator system. The condenser Q, permits the oscillatingcurrents to flow from the oscillator through that portion of the inductance C as indicated by'the adjustable taps.

in accordance with this invention an additional potential derived from a source of high frequency voltage is applied to the shield H of amplifier valve D, that is to the input side or circuit of said valve. In this instance the additional potential is obtained from the transformer formed by the inductance C and the inductively related coil R, Which latter is connected in circuit with the shield H of valve D as shown. The source of additional potential for shield H is thus the oscillating valve D, altl'iough it would perhaps be more correct to say that the Whole oscillator system, is the source of such potential.

S represents, in this'instance, a telephone transmitter, and T is the local battery, the

circuit of the telephone being coupled hrough, the transformer U to the shield H of amplifier D, and the condenser V is for the purpose of pern'iitting the additional source of potential represented by the transformer CR, to be applied directly between the shield H and filai'nent E of valve D.

I have found that With some types of shield valves, where practically no amplification could be ol'itained Without the additional source of potential, using the valve as an amplifyin modulator, the addition of a source of high frequency potential produced excellent amplification] Fig. 2 illustrates the invention apphed to a. shield valve used as a detector. Typical circuits are shown coupled to the antenna A.

The shield 'H of the valve is included as shown in the circuit of the coupling coil N former Z, the secondary of which is shunted ceiver.

by a condenser a. I

In Fig. 3 the invention is shown in connection with the amplifier circuits of a re The output circuit of valve D is coupled to the input circuit of valve D in any suitable manner as by means of the resistance coupling 6, and in this instance the plate battery X supplies both valves. The alternating current generator Z furnishes additional high frequency potential for the shield ll of valve D and a similar generator Z is coupled to the shield H of valve D through the transformer Z Fig. l is a modification in which the invention is shown in connection with a three element valve D as a detector having an internal grid H to which the additional high frequency potential is applied from the source in. In the circuits, Z) represents the usual grid condenser and the resistance 0 forming a leak may be used if desired.

1. claim and desire to obtain by Letters Patent the following:

1. The method of controlling the electron stream between the anode andcathode of a vacuum tube which consists in applying an alternating potential to a surrounding exterior control electrode, controlling thereby the electron charge upon the interior surface of aid tube, and applying to the control electrode, a high frequency alternating potential and thereby increasing the efl'ective ness of the control upon the electron stream of the first mentioned alternating potential.

in a high. frequency signaling system, in combination an oscillator vacuum tube and a cooperating amplifying vacuum tube, respectively having extelrnall surrounding control electrodes, means for applying alternating potentials thereto, and means for applying a second high frequency alternating potential to one thereof.

3. In high frequency signaling systems, in combination a coupled vacuum tube arrangement comprising a pair of cooperating vacuum tubes having internal anode and cathode electrodes and external control electrodes, and means associated with the input circuit of one thereof for applying an auxil iary high frequency alternating potential thereto for iiicreasing the amplification constant thereof,

In testimony whereof I have signed this specification. 

